1. Field of the Invention
The present invention relates to an electron beam generator or an electron gun suitable for use in a lithography device.
2. Description of the Prior Art
A lithography device (electron beam writer) is described in U.S. Pat. No. 4,724,328 having an electron-optical column including a control diaphragm for generating a plurality of electron probes, which can be individually deflected or blanked. The structural details of the control diaphragm are described in published European application No. 0 191 439. The control diaphragm basically consists of a silicon disc, having a central portion fashioned as a self-supporting membrane, and being provided with a grid of square recesses. An electrode system arranged in the region of the recesses serves as the deflection unit. In order to use the available source current in an optimal fashion, a ribbon-shaped electron beam is made to be incident on the control diaphragm. The electron beam is generated using optics including a cylinder lens and a condenser lens, both lenses being disposed in the path of the electrons between the electron source and the diaphragm. The electron source or emitter may be a LaB.sub.6 knife-edged cathode.
It is a problem in the art to provide an electron beam generator for use as described above wherein a ribbon-shaped object, such as a diaphragm with a grid of recesses, can be uniformly irradiated by the electron beam.